This study assessed the effect of autoimmune diseases on mortality among women. Counts of autoimmune disease deaths were compared with frequencies of the 10" official" leading causes of death among women in the United States in 1995. Autoimmune disease deaths exceeded the frequency of the 10th leading cause in every age category of women younger than 65 years and exceeded that for the eighth leading cause in the 15 to 24, 25 to 44, and 45 to 64 years age groups. Autoimmune diseases constitute a leading cause of death among young and middle-aged women. This fact is obscured by current methods used to identify leading causes.